P690: GENE MUTATIONAL PROFILE ASSOCIATED WITH TREATMENT FAILURE OR PROGRESSION IN CHRONIC MYELOID LEUKEMIA
Authors: N. Estrada, B. Xicoy, M. Cabezón, S. Marcé, A. Senin, A. Angona, E. Alonso, M. Ratia, M. E. Plensa, J. Buch, X. Ortín, L. Zamora
Journal: HemaSphere (2022)

Background: Approximately one third of chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKI) fail to achieve optimal response due to resistance. It is known that BCR-ABL1 kinase domain (KD) mutations are associated with TKI resistance. However, only half on non-responsive patients carry BCR-ABL1 KD mutations. Other resistance mechanisms independent of BCR-ABL1 KD mutations, such as mutations in myeloid-related genes, may participate in the lack of response. Moreover, resistance to TKI therapy confers a much higher risk of progression to advanced disease stages of CML, such as accelerated phase (AP) and blast crisis (BC), and consequently, a worse prognosis. Aims: The main objective of this study was to explore the impact of mutations in myeloid-related genes in TKI resistance and progression to AP/BC by targeted deep-sequencing (TDS). Methods: The mutation profile study was done by TDS using a 32 myeloid-related gene panel (Myeloid Solution Capture Kit, Sophia Genetics, Switzerland). The platform Sophia DDM (Sophia Genetics) was used for data analysis. Regarding variant filtering, sequencing and mapping errors were eliminated and intronic and synonymous variants were filtered out. Variants present with a minor allele frequency (MAF) >1%, according to population databases (ExAc, 1000 genomes), were considered polymorphic changes without clinic relevance. COSMIC, VARSOME and Franklin databases as well as in silico functional predictors (SIFT, PolyPhen2 and MutationTaster) were used for variant interpretation. Variants were also filtered according to the variant allele frequency (VAF): all variants with VAF ≥5% were reported, as well as hot-spot variants with VAF 2-5% and at least 25 reads. Only variants described as pathogenic or potentially pathogenic were reported. Finally, BCR-ABL1 mutations were analyzed by Sanger in resistant patients. Results: TDS was performed in a total of 78 samples from 67 patients. Across patients with available sample at diagnosis, 25% (16/64) of patients harbored at least one mutation. Overall, 11 (17.2%) patients had 1 mutation, 3 (4.6%) had 2 mutations, 1 (1.6%) patient had 3, and 1 (1.6%) patient had 4 mutations (Figure 1A). Most frequently mutated genes at diagnosis were ASXL1 (14.1%), DNMT3A (6.3%), JAK2 (3.1%) and TET2 (3.1%), followed by ETV6, EZH2, IDH2, SETBP1, SRSF2, TP53 and WT1, all of them at a frequency of 1.6% (Figure 1B). Of the 67 CML patients included, 15 (22.4%) had resistance to first-line TKI and 5 of them (33%) progressed to AP/BC. From the 15 resistant patients, TDS was performed in 12 cases at diagnosis, in 5 at time of resistance, and at progression in 4/5 patients. At diagnosis, 6 (50%) resistant patients harbored 1 mutation in ASXL1 (3/12), DNMT3A (2/12) or TET2 (1/12) and 1 patient harbored 2 mutations (ASXL1 and WT1). Only 9 of 52 (17.3%) non-resistant patients harbored ≥1 mutation at diagnosis; most frequently mutated gene was ASXL1 (5/9). At time of resistance, 5 patients had BCR-ABL1 mutations by Sanger technique and 3 patients harbored cancer-related gene mutations by TDS (ASXL1 in 2 patients). At progression, all patients harbored at least 1 mutation by TDS, except one patient in which only 2 mutations in BCR-ABL1 KD were detected. Image:Summary/Conclusion:ASXL1 mutation was the most frequent mutation in CP at diagnosis and ASXL1 and ABL1 were the most common variants at resistance and progression. Acquisition of mutations was detected during CML progression. Acknowledgments: this work was supported by a grant from Incyte (EU-ES-H-18021)